The physicochemical degradation of Indigo Carmine (IC) dye in aqueous solution was performed using single and combined Advanced Oxidation Processes (AOP's). Photocatalysis (TiO 2-UV), Ozonation (O 3) and Sonolysis (SN) were tested either in a standalone methodology or by combination of two simultaneous AOP's. The dye conversion was followed by both measurements: 1) color removal determined by UV-VIS spectrometry and 2) organic and inorganic load determined by the chemical oxygen demand (COD). A complete and quick color disappearance of model water waste has been obtained by using combination of non-irradiated AOP's, namely, O 3 /SN, which contrasts to the combination of irradiated photocatalysis with O 3 or sonolysis. Color removal with simultaneous TiO 2-UV/SN reached 77% while TiO 2-UV/O 3 reached 96% at similar reaction time. On the other hand, the standalone O 3 yielded the highest color removal (94.4%) in 32 minutes whereas SN reached only 39.2% in 4 hours. The standalone light irradiated TiO 2-UV reached 93.3% color removal in one hour of reaction time. These results indicated that non-irradiated (SN and O 3) enhance synergistic effects that provoke structural changes in dye molecule without reaching total degradation. This is evidenced from FTIR of residuals from reaction mixture in which it has been observed the presence of organic molecules such as aromatics, sulfonic and amines refractory compounds that are mechanistically possible to be found during IC degradation. Also, toxicity tests (MicroTox® Technique) were performed using commercially available bacteria culture before and after IC degradation for each AOP and their combination. Reduction of aqueous dye concentration decreased the level of toxicity of the treated water which is the main target of the AOP's but the presence of the remaining recalcitrant compounds have also toxic effect.
Abstract-This paper describes the degradation of red anthraquinone dyes (alizarin, alizarin S and alizarin complexone) with initial concentration of 100 ppm in aqueous solution by ozone oxidation. The results of UV/VIS and FTIR spectra showed that the anthraquinone structures, nitrogen linkages and amino groups of anthraquinone dyes were broken after the direct ozone reaction. Almost complete color removal was obtained through ozonation within about 70, 18 and 18 min, reaction time for alizarin, alizarin S and alizarin complexone, respectively. The analysis of residuals by FTIR indicated that the alizarin primary degradation products were some organic compounds (e.g., aromatic groups, carbonate esther) and CO 3 2-(due to the dye mineralization). Alizarin S degradation products exhibited IR absorption bands at 1717, 1623, 1387, 1105 and 1045 cm -1 , attributed to >C=O (carbonyl), >C=C< (alkenes), -C-C-C (alkanes), SO 4 2-and -C-O-C-groups respectively. Approximately 90% of alizarin can be removed from water streams with the present methodology; followed by approximately 80% removal of complexone and 70% removal of alizarin S.
The experimental degradation of a water soluble dye, potassium indigo tetrasulfonate salt, has been studied using stand-alone ozonation and photocatalytic oxidation process. Progress of the dye oxidation was followed by UV-VIS spectrophotometric measurements at controlled operating conditions. The organic content of reaction samples was measured to verify the process efficiency in dye mineralization. According to current results, almost complete color removal was obtained for ozonation within about 1 h reaction time. The reduction of the organic load was almost 80% from its original while initial sulphur content decreased to 32.5%. Dye conversion of 100% was obtained by means of a photocatalytic process using TiO2 as catalyst at 294 nm irradiated UV light. This complete color removal for the catalytic process was observed within 7 min of reaction time. The calculated initial rate of reaction of photocatalysis treatment was 8 times faster than that of ozonolysis. However, the remaining organic load of photocatalysis was almost 88% from its original while the final sulphur content was 27.3%. This contrasting behavior of the performance of the type of oxidation process stressed importance of physicochemical phenomena and intermediates molecules present during dye degradation. An insightful and mechanistic aspect of the dye oxidation was developed by performing quantumchemical calculations.
Abstract-The HKUST-1 copper metal organic framework (MOF) is one of the most studied MOFs because it has high pore volume, a large surface area, high chemical stability and also the ability to bind water, among other molecules, by coordinating to the unsaturated Cu(II) sites. In this study we propose two strategies for the elimination of two dyes from aqueous solution employing HKUST
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